RNA polymerase II subunit A C-terminal domain phosphatase (CTDP1)

Processively dephosphorylates'Ser-2' and'Ser-5' of the heptad repeats YSPTSPS in the C-terminal domain of the largest RNA polymerase II subunit. This boosts the action of RNA polymerase II.

Plays a role in the exit from mitosis by dephosphorylating crucial mitotic substrates (USP44, CDC20 and WEE1) which are needed for M-phase-promoting factor (MPF)/CDK1 inactivation. .